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V-1257 — Vacuum Gas Oil Column V-1257

Delayed Coker · Vacuum Gas Oil service · Installed Aug 30, 1995 (31 yrs in service)

High
Current Min. Thickness
1.525 in
t-min 1.834 in
Measured Corrosion Rate
15.06 mpy
ML-predicted: 16.42 mpy
Remaining Life
0.0 yrs
Next Inspection Due
Feb 20, 2027
Interval: 0.5 yrs (API 510)

UT Thickness Trend

Minimum CML reading per inspection vs. ASME Sec. VIII t-min

Vessel Specification

MaterialSA-240-316L Stainless
Design CodeASME BPVC Section VIII, Div. 2
Joint Efficiency0.85
Design Pressure448 psig
Design Temperature189 °F
Operating Pressure317 psig
Operating Temperature143 °F
Diameter114 in
Nominal Thickness2.015 in
Corrosion Allowance0.1250 in
H2S / Chloride48 / 58 ppm
Flow Velocity12.4 ft/s
Process pH7.56
InsulatedYes

Corrosion & Remaining-Life What-If

Adjust operating conditions to see the live model-predicted corrosion rate and implied remaining life

Live Prediction — What-If Model
13.24 mpy
Predicted corrosion rate under these conditions (-1.82 mpy vs. current measured rate)
Implied Remaining Life
0.0 yrs
Implied Reinspection Interval
0.5 yrs

What-if model: standardized Ridge regression, R² 0.56 on held-out fleet data (3.25 mpy MAE). Runs entirely client-side for instant feedback — see Model Insights for the full fleet-scale ensemble model used for official predictions.

Governing Damage Mechanism — Naphthenic Acid Corrosion

API 571 §4.2.10

Aggressive, velocity-assisted corrosion in high-TAN crude fractions, most severe 450–750°F; low-alloy/carbon steel is far more susceptible than Mo-bearing or 316 SS.

Recommended inspection approach: UT thickness at high-velocity/turbulent locations; feed TAN monitoring; consider alloy upgrade per API 571 guidance.

Inspection History

UT thickness readings, most recent first

DateMethodCML CountAvg ThicknessMin CML Thickness
Aug 22, 2026UT Spot61.5452 in1.5253 in
Oct 18, 2024UT Grid (API 572)61.5759 in1.5685 in
Nov 28, 2022UT Spot61.6009 in1.5984 in
May 11, 2021UT Grid (API 572)61.6295 in1.6184 in
Mar 14, 2018UT Grid (API 572)61.6760 in1.6758 in
Aug 29, 2015UT Spot61.7113 in1.7112 in
Aug 10, 2013UT Grid + RT61.7431 in1.7426 in
Jul 13, 2010UT Spot61.7918 in1.7721 in
Oct 30, 2008UT Spot61.8171 in1.8030 in
Nov 30, 2006UT Grid + RT61.8443 in1.8284 in
Apr 8, 2005UT Spot61.8700 in1.8627 in
Jun 1, 2003UT Grid + RT61.8976 in1.8779 in
Nov 3, 2000UT Spot61.9361 in1.9248 in
Jul 4, 1998UT Grid (API 572)61.9680 in1.9561 in
Feb 19, 1997UT Grid (API 572)61.9921 in1.9754 in